Sheep able to sense human emotion through odors?

Humans are integral part of the environment of domestic animals. But how do they perceive us, and to what extent can they detect our emotional states?

We already know that mice (Destrez et al., 2021), dogs (D'Aniello et al., 2018), cats (D'Ingeo et al., 2023), horses (Sabiniewicz et al., In 2020, Jardat et al. 20023) and cows (Destrez et al., 2021) react differently to the body odors of humans who are either negatively or positively stressed. This leads us to an exciting possibility: the emotional state of humans might be transmitted by scent to animals! This phenomenon is called “emotional contagion”. However, this olfactory mediation of emotions remains poorly studied in farm animals.

In order to examine whether emotional human odors affect sheep behavior, two types of axillary sweat (collected from 34 students aged 20 to 38) were presented to them: one collected after an exam (“stress” odor), the other after a class (“non-stress” odor). Presented to ewes and rams during a discrimination test, these two chemo-stimuli induced behaviors indicating their discrimination, but not necessarily reflecting the emotional state (stress or non-stress) of the donors.

Overall, sheep perceive the odors of unfamiliar humans and discriminate between their stress and non-stress axillary odors. However, at least under our experimental conditions, these two emotional types of human odors do not elicit a congruent response (the human stress odor does not induce a sheep stress response). This preliminary study needs to be replicated under revised experimental conditions, in particular by presenting human odors produced under more extreme stress, in a nonfeeding behavioral test (see photo), and taking into account the sheep's donors' familiarity level. In any case, assessing the impact of the perception of human emotional odors by farm animals is important for improving human-animal trust.